local finished = false
local n = 0
local orientation = 0

function d()
    return turtle.detect()
end

function dd()
    return turtle.detectDown()
end

function l()
    turtle.turnLeft()
    orientation = orientation - 90
    if (orientation == -360) then
        orientation = 0
    elseif (orientation == -270) then
        orientation = 90
    end
end

function r()
    turtle.turnRight()
    orientation = orientation + 90
    if (orientation == 360) then
        orientation = 0
    elseif (orientation == 270) then
        orientation = -90
    end
end

function f()
    turtle.forward()
end

function b()
    turtle.back()
end

function selectBuildMaterial()
    local foundBuildMaterial = false
    local buildMaterialIndex = 1
    for i = 1, 16 do
        turtle.select(i)
        if (not turtle.refuel(0)) and (not foundBuildMaterial) and (turtle.getItemCount() > 0) then
            foundBuildMaterial = true
            buildMaterialIndex = i
        end
    end

    if not foundBuildMaterial then
        finished = true
    else
        turtle.select(buildMaterialIndex)
    end
end

function refuel()
    local foundFuel = false
    for i = 1, 16 do
        turtle.select(i)
        if turtle.refuel(0) and (not foundFuel) then
            turtle.refuel(1)
            foundFuel = true
        end
    end

    if not foundFuel then
        finished = true
    end

    selectBuildMaterial()
end

while not finished do
    if (turtle.getFuelLevel() <= 0) then
        refuel()
    end

    if (orientation ~= 0) then

        if (orientation < 0) then
            r()
            if d() then
                l()
            else
                f()
                if dd() then
                    b()
                    l()
                else
                    b()
                end
            end
        elseif (orientation > 0) then
            l()
            if d() then
                r()
            else
                f()
                if dd() then
                    b()
                    r()
                else
                    b()
                end
            end
        end

    end

    if d() then
        r()
        if d() then
            l()
            l()
            if d() then
                finished = true
            else
                f()
                if dd() then
                    finished = true
                end
            end
        else
            f()
            if dd() then
                b()
                l()
                l()
                if d() then
                    finished = true
                else
                    f()
                    if dd() then
                        finished = true
                    end
                end
            end
        end
    else

        f()

        if dd() then
            b()
            r()
            if d() then
                l()
                l()
                if d() then
                    finished = true
                else
                    f()
                    if dd() then
                        finished = true
                    end
                end
            else
                f()
                if dd() then
                    b()
                    l()
                    l()
                    if d() then
                        finished = true
                    else
                        f()
                        if dd() then
                            finished = true
                        end
                    end
                end
            end
        end

    end


    if (turtle.getItemCount() <= 0) then
        selectBuildMaterial()
    end

    turtle.placeDown()

    n = n+1

    if n>10000 then
        finished = true
    end

end